Central problems in wireless communications are for example: how to improve the spectral efficiency, how to improve the system throughput, how to improve the link budget, how to reduce the required transmission power, how to reduce the interference in the system and how to select for one connection a proper momentary transmission mode from several possible transmission modes.
Most commonly used solutions to above-mentioned problems are sectorisation, beamforming (BF), different kind of diversity methods, multi-antenna techniques such as MIMO and adaptive radio link techniques. For example in WiMAX (Worldwide Interoperability for Microwave Access) and UMTS/LTE (Universal Mobile Telecommunications Services/Long Term Evolution) future roadmaps include multi-antenna techniques which apply extensively feedback from the mobile terminal in the so-called preceding approach for improving the radio link performance. In the preceding approach it is possible to combine beamforming and MIMO. The proposed system operates in a following way. The receiving mobile terminal estimates a down link radio channel (DL) and based on that information the mobile terminal directs a serving base station (BS) to apply different beamforming weights to the signals of different antennas. These techniques are still in a research mode and address to the WiMAX AAS/AMC (Adaptive Antenna Systems/Adaptive Modulation and Coding) modes which are not yet fully implemented in the WiMAX standards. The future AAS /AMC techniques increase complexity of the mobile terminal.
However, the basic commercial WiMAX mobile terminals do not support the advanced beam-forming and MIMO techniques. Therefore, there exists a need for a method by which a prior art WiMAX base station could select the most suitable transmission mode for each downlink transmission momentarily to a prior art WiMAX mobile station. The same problem is encountered with UMTS and 3GPP LTE base stations.